Rust streaks.

Stage 3 of the bastion will need some rusty streaking!!  This is very similar to adding depth to flat surfaces, you will need oils, red, orange and brown.
On your palette you will have to mix them to get a similar colour as your rust. You will need two brushes, one small one to apply the oils and one to rub off the the excess and streak the paint.

Take your mix and then apply to the areas where you want the streaking to start.

Now its simply a case of taking the clean medium soft brush and dipping it in some turpentine and rubbing off the excess.  Now simply drag the oil in the direction you want to streak, if its too strong just keep removing the paint with soft downward strokes. If you dont like it at all then just load up with turps and rub it off completely. When your done you should end up with something like this.

Sorry again for the bad photography  but you get the idea.  For ultra realism you can add a little pigment to the tops of the streaks do add more tones.  By also copying this with a buff/white mix of oil paint you can get some awsome water marks too! See its easy?! Better pics will come with the mud pigments. Hopefully.